| 2003 |
Cytosolic chaperones Hsp90 and Hsp70 dock onto a specialized TPR domain in Tom70 at the outer mitochondrial membrane, delivering preproteins to the receptor for subsequent membrane translocation dependent on the Hsp90 ATPase. Disruption of chaperone/Tom70 recognition inhibits preprotein import into mitochondria. In mammals Hsp90 is used; in yeast Hsp70 is the primary partner. |
Co-immunoprecipitation, cross-linking, in vitro import assay, purified cytosolic fragment of Tom70 |
Cell |
High |
12526792
|
| 1997 |
The purified cytosolic domain of Tom70 preferentially binds preproteins with internal targeting signals (not N-terminal presequences), and a synthetic presequence peptide does not compete for Tom70 binding (unlike Tom20/Tom22), demonstrating distinct binding specificity among import receptors. |
Purified recombinant cytosolic receptor domains, in vitro preprotein binding assay, competition with synthetic presequence peptide |
The Journal of biological chemistry |
High |
9252394
|
| 1999 |
Tom70 binds to multiple segments within internal-targeting-signal-containing preproteins (e.g., phosphate carrier) distributed throughout the mature protein, but does not efficiently bind presequence segments. Both charged and uncharged peptides serve as Tom70 binding sites, indicating charge is not a critical determinant of internal targeting sequences. |
Cellulose-bound peptide scans (SPOT synthesis), binding of purified cytosolic receptor domains to overlapping 13-mer peptides |
The Journal of biological chemistry |
High |
10347216
|
| 2000 |
A stably folded 25 kDa core domain in the middle portion of Tom70, containing two of its seven TPR motifs, is sufficient for binding non-cleavable and cleavable preproteins with internal targeting signals with the same specificity as full-length receptor. Competition studies showed at least one additional interaction site exists in full-length Tom70. |
Domain deletion/truncation, recombinant protein expression and purification, preprotein binding competition assay |
Journal of molecular biology |
High |
11054285
|
| 2006 |
Hsp90 plays a role in import steps subsequent to Tom70 targeting: geldanamycin (N-terminal ATP-site inhibitor) had no effect on preprotein-Hsp90 interactions or Hsp90 docking onto Tom70 but impaired formation of preprotein import intermediates at the outer membrane, whereas novobiocin (C-terminal inhibitor) blocked Hsp90 cross-linking to preprotein and co-precipitation with Tom70. |
Hsp90 inhibitor treatment (geldanamycin, novobiocin), cross-linking, co-precipitation with purified cytosolic Tom70 fragment, in vitro import assay |
The Journal of biological chemistry |
High |
16968702
|
| 2007 |
Multiple Hsp40-related J-domain proteins (DJA1, DJA2, DJA4) specifically bind preproteins (via their C-terminal regions) and cooperate with Hsc70 and Hsp90 in Tom70-dependent mitochondrial import. DJA dominant-negative mutants lacking J-domains blocked Hsc70 binding to preprotein and impaired mitochondrial import. The Hsp90 cochaperones p23 and Aha1 also regulated Hsp90-preprotein interactions. |
Mass spectrometry identification of chaperone complexes, dominant-negative mutant expression, Hsc70 ATPase activation assays, in vitro import assay in HeLa cells |
Molecular biology of the cell |
High |
17596514
|
| 2009 |
Tom70 recognizes a set of presequence-containing precursor proteins whose mature regions are aggregate-prone; the receptor domain of Tom70 prevents aggregate formation of these substrates, maintaining their solubility for efficient transfer to downstream import machinery. Tom70 thus functions as a docking site for both cytosolic chaperones and aggregate-prone substrates. |
Proteome-wide in vitro import assay, aggregation prevention assay with purified Tom70 receptor domain |
The Journal of biological chemistry |
High |
19767391
|
| 2009 |
Analytical ultracentrifugation and SAXS reveal that the cytosolic domain of Tom70 exists as an elongated monomer. Fluorescence anisotropy shows the monomer can simultaneously bind chaperone and precursor peptides; chaperone binding does not alter preprotein affinity or detectable shape change in the monomer. Molecular modeling indicates chaperone binding is incompatible with Tom70 dimer formation. |
Analytical ultracentrifugation, solution SAXS, fluorescence anisotropy, molecular modeling |
Journal of molecular biology |
High |
19358854
|
| 2010 |
Human Tom70 functions as a monomer; the cytosolic fragment exists in equilibrium between monomer and dimer. A point mutation at the predicted dimer interface increased monomeric fraction and significantly enhanced preprotein targeting, whereas chaperone docking was unchanged. Cross-linking of full-length Tom70 on mitochondrial membranes shows little evidence of homodimers, indicating monomers are the functional unit. |
Analytical ultracentrifugation, cross-linking, size-exclusion chromatography, multi-angle light scattering, site-directed mutagenesis, in vitro preprotein targeting assay |
The Biochemical journal |
High |
20504278
|
| 2010 |
Tom70 interacts with MAVS upon RNA virus infection and recruits TBK1/IRF3 to mitochondria via binding of Tom70's clamp domain (R192) to the C-terminal EEVD motif of Hsp90. Disruption of this interaction or mislocalization of Tom70 sharply impairs TBK1 and IRF3 activation. Tom70 acts as a critical adaptor linking MAVS to TBK1/IRF3. |
Co-immunoprecipitation, ectopic expression, siRNA knockdown, domain mutation (R192), reporter gene assay for IRF3-mediated gene expression |
Cell research |
High |
20628368
|
| 2011 |
Tom20 interacts with the TPR clamp domain of Tom70 via a conserved C-terminal DDVE motif, competing with the chaperones Hsc70 and Hsp90 for Tom70 binding. This interaction was detected by cross-linking of endogenous proteins on HeLa mitochondria, co-precipitation, and NMR titrations. The functional interaction may facilitate preprotein release from chaperones by competition, constituting a chaperone displacement mechanism. |
Protein cross-linking on mitochondria, co-precipitation, NMR titration, surface plasmon resonance, site-directed mutagenesis of TPR clamp domain and DDVE motif |
The Journal of biological chemistry |
High |
21771790
|
| 2015 |
Tom70 directly binds presequence peptides via a dedicated groove. A single point mutation M551R in this pocket reduces presequence binding affinity ten-fold and selectively impairs import of presequence-containing precursor Mdl1, but not the ADP/ATP carrier, demonstrating that Tom70 contributes to the presequence import pathway. |
Fluorescence binding assay with presequence peptides, site-directed mutagenesis (M551R), in vitro import assay |
Biochimica et biophysica acta |
High |
25958336
|
| 2016 |
Cross-linking/mass spectrometry identified a novel region of contact between the C-terminal domain of Hsp90 and Tom70 beyond the canonical MEEVD/TPR interaction. A molecular model validated by SAXS and hydrogen/deuterium exchange indicates only one MEEVD motif within dimeric Hsp90 contacts Tom70. ITC confirmed the secondary interaction site affects preprotein import. |
Cross-linking/mass spectrometry, isothermal titration calorimetry, SAXS, hydrogen/deuterium exchange mass spectrometry, in vitro mitochondrial import assay |
The Journal of biological chemistry |
High |
27402847
|
| 2018 |
Many preproteins contain internal MTS-like signals (iMTS-Ls) in their mature regions that mediate binding to Tom70. Using Atp1 as model substrate, iMTS-Ls mediate Tom70 binding and can target proteins to mitochondria when presented at the N-terminus. Import of preproteins with high iMTS-L content is significantly impaired in the absence of Tom70, supporting a stepping-stone model where Tom70-mediated internal binding improves import efficiency. |
In silico prediction of iMTS-Ls, in vitro import assay with Tom70 deletion, N-terminal fusion targeting experiments, binding assay |
The Journal of cell biology |
High |
29382700
|
| 2018 |
TOM70 clusters in distinct OMM foci that frequently overlap with ER-mitochondria contact sites. TOM70 depletion specifically impairs IP3-linked ER-to-mitochondria Ca2+ transfer by interacting with IP3 receptors (IP3R3) and favoring their functional recruitment close to mitochondria. Reduced constitutive Ca2+ transfer dampens mitochondrial respiration, affects bioenergetics, induces autophagy, and inhibits proliferation. TOM20 depletion did not reproduce this phenotype. |
Live-cell imaging/super-resolution microscopy for localization, siRNA knockdown, Ca2+ imaging, co-immunoprecipitation with IP3R3, mitochondrial respiration assay |
Current biology : CB |
High |
29395920
|
| 2021 |
The PERK kinase promotes cristae formation by increasing TOM70-assisted mitochondrial import of MIC19 (a MICOS complex subunit). Cold stress/β-adrenergic stimulation activates PERK, which phosphorylates OGT; phosphorylated OGT O-GlcNAcylates TOM70 on Ser94, enhancing MIC19 protein import and promoting cristae formation and respiration. CK2α-mediated phosphorylation of TOM70 Ser94 opposes this by decreasing MIC19 import. |
In vivo and in vitro reconstitution, OGT glycosylation assay, site-directed mutagenesis (Ser94), in vitro mitochondrial import assay, cryo-EM of cristae, genetic epistasis with PERK/OGT/CK2α |
Cell metabolism |
High |
33592173
|
| 2021 |
Crystal structure of SARS-CoV-2 Orf9b in complex with the cytosolic segment of human TOM70 resolved to 2.2 Å. A central helical portion of Orf9b occupies the deep hydrophobic pocket of TOM70 C-terminal domain (CTD). The Orf9b dimer does not bind TOM70, but a monomeric C-peptide of Orf9b binds with nanomolar affinity (ITC). Orf9b binding to TOM70 CTD allosterically reduces Hsp90 EEVD binding to TOM70 NTD by ~29-fold, providing a structural mechanism for immune evasion. |
X-ray crystallography (2.2 Å), isothermal titration calorimetry, synthetic peptide binding assay |
Nature communications |
High |
33990585
|
| 2021 |
The predominant function of Tom70 in vivo is to recruit cytosolic chaperones to the outer mitochondrial membrane, rather than to serve as a mitochondrion-specifying targeting receptor. Tethering an unrelated chaperone-binding domain onto the mitochondrial surface complemented most defects caused by Tom70 deletion, including reduction of proteotoxicity of hydrophobic inner membrane proteins. The chaperone-binding activity protects the cytosol from mitoprotein-induced stress. |
In vivo high-content screens, in vitro import experiments, Tom70 deletion combined with heterologous chaperone-binding domain tethering, proteotoxicity assays |
Cell reports |
High |
33826901
|
| 2021 |
SARS-CoV-2 Orf9b binding to TOM70 inhibits Hsp90 recruitment to TOM70 and suppresses downstream chaperone-associated signaling. Orf9b Ser53 and TOM70 Glu477 are crucial residues for Orf9b-TOM70 association; the phosphomimetic Orf9b S53E shows drastically reduced TOM70 binding and does not inhibit Hsp90 recruitment, indicating phosphorylation regulates complex formation. A second binding site at the TOM70 N-terminal TPR domain was also identified. |
Site-directed mutagenesis, co-precipitation, chaperone recruitment assay, phosphomimetic variant analysis |
International journal of molecular sciences |
Medium |
34502139
|
| 2013 |
Tom70 is essential for PINK1 import into mitochondria. Using a cell-free import system, PINK1 import was found to depend on Tom70 but not on Tom40 (the main import channel). PINK1 is not processed by the mitochondrial processing peptidase, indicating a unique import pathway that is independent of the TOM core complex but requires Tom70. |
Cell-free mitochondrial import assay, Tom70 knockdown, Tom40 knockdown/depletion, processing peptidase assay |
PloS one |
Medium |
23472196
|
| 2006 |
Mcl-1 interacts with the mitochondrial import receptor Tom70 via an internal EELD domain. A Tom70 antibody blocking Mcl-1-Tom70 interaction inhibits mitochondrial import of Mcl-1 in vitro. Tom70 knockdown significantly reduces Mcl-1 mitochondrial targeting; mutation of the EELD motif attenuates Tom70 binding and mitochondrial targeting. |
Co-immunoprecipitation, in vitro import assay with blocking antibody, siRNA knockdown, site-directed mutagenesis of EELD motif |
Molecular biology of the cell |
Medium |
16822835
|
| 2015 |
Tom70 recruits IRF3 to mitochondria via Hsp90 upon Sendai virus infection, forming a dynamic complex Tom70/Hsp90/IRF3/Bax. Bax interacts specifically with IRF3 upon virus infection, and relocation of Bax to mitochondria via this complex induces cytochrome c leakage and apoptosis. IKK-i is essential for this apoptosis whereas TBK1 is dispensable. |
Co-immunoprecipitation, subcellular fractionation, cytochrome c release assay, siRNA knockdown, ectopic expression |
Journal of virology |
Medium |
25609812
|
| 2002 |
Rat Tom70 (OM70) functions as a receptor for preproteins with internal targeting signals (ADP/ATP carrier, rTOM40) but not for cleavable presequence-containing proteins. Blue native PAGE and immunoprecipitation show OM70 is loosely associated with the ~400 kDa TOM complex containing rTOM22 and rTOM40. Yeast two-hybrid showed OM70 interacts with rTOM20 and rTOM22 through cytoplasmic domains. The N-terminal 66-residue region including a transmembrane domain and arginine cluster is sufficient for mitochondrial targeting. |
Antibody inhibition of import, blue native PAGE, immunoprecipitation, yeast two-hybrid, in organello import assay |
Journal of cell science |
Medium |
11956321
|
| 2011 |
Stoichiometry analysis revealed that one monomer of Tom70 interacts per dimer of the C-terminal domain of Hsp90 (containing the EEVD motif), with a KD of ~360 nM. This stoichiometry and thermodynamic profile differ from those of other TPR co-chaperones, indicating a distinct interaction mechanism between Tom70 and Hsp90. |
Isothermal titration calorimetry, size-exclusion chromatography, biophysical analysis |
Archives of biochemistry and biophysics |
Medium |
21781956
|
| 2007 |
In yeast, Tom70 and its paralogue Tom71 are required for localization of the soluble F-box protein Mfb1 to mitochondria. Mfb1 interacts with Tom71 in vivo and binds to mitochondria through Tom70 in vitro. Cells lacking both Tom70 and Tom71 display aberrant mitochondrial morphology (short tubules and aggregates) similar to mfb1-null mutants, revealing an unexpected role for Tom70 in recruiting soluble proteins to the mitochondrial surface. |
In vivo co-immunoprecipitation (Mfb1-Tom71), in vitro mitochondrial binding assay, fluorescence microscopy of mitochondrial morphology, gene deletion |
EMBO reports |
Medium |
18007655
|
| 2022 |
In budding yeast, Tom70 moonlights as a transcriptional regulator of mitochondrial protein genes, and this transcription-regulatory role is conserved in Drosophila. The dual roles in transcription and import allow cells to coordinate mitochondrial biogenesis without compromising cytosolic proteostasis. Age-related reduction of Tom70 is associated with loss of mitochondrial membrane potential, mtDNA, and mitochondrial proteins; Tom70 overexpression extends replicative lifespan. |
Genetic deletion and overexpression, transcriptional reporter assays, Drosophila genetic experiments, mitochondrial membrane potential and mtDNA measurements |
eLife |
Medium |
35234609
|
| 2025 |
The 2.04 Å crystal structure of unliganded human TOM70 cytosolic domain reveals two distinct conformations—open and closed—within the asymmetric unit. HDX-MS and MD simulations confirm these states in solution. Network analyses identify a continuum of motion linking the NTD (chaperone-binding) and CTD (preprotein-binding) via helices α7, α8, and α25. Orf9b engagement of the CTD interrupts this allosteric network, stabilizing a partially-closed intermediate and dampening NTD dynamics. |
X-ray crystallography (2.04 Å), hydrogen-deuterium exchange mass spectrometry, molecular dynamics simulations, principal component analysis, dynamical network analysis |
Structure |
High |
41386227
|
| 2025 |
The cytosolic chaperone PPID (cyclophilin 40/Cyp40) drives OMM insertion of TOM70 via its PPIase activity and C-terminal tetratricopeptide repeats, which show specificity towards TOM70 core and C-tail domains. This PPID-mediated TOM70 insertion regulates thermogenic/respiratory function in brown adipocytes and protects against diet-induced obesity in mice. |
In vitro reconstitution of OMM insertion, domain mutagenesis (PPIase activity mutation, TPR deletion), brown adipocyte functional assays, mouse obesity model |
Nature cell biology |
High |
39753947
|
| 2025 |
In zebrafish, a missense mutation in tomm70 (affecting a conserved isoleucine corresponding to human TOMM70 p.Ile554Phe) impairs the interaction of Tomm70 with the ER sterol transporter Lam6, impairs mitochondrial transport to axons and dendrites, and causes demyelination of large-calibre spinal cord axons. These defects recapitulate features of hereditary spastic paraplegia. |
Zebrafish missense mutant model, co-immunoprecipitation (Tomm70-Lam6 interaction), fluorescence microscopy of mitochondrial axonal transport, electron microscopy of myelin |
Disease models & mechanisms |
Medium |
40151845
|
| 2022 |
ORF9b forms a complex with TOM70 that prevents full-length Hsp90 from binding to TOM70. The isolated C-terminal domain of Hsp90 is also blocked by ORF9b occupying TOM70. Biophysical characterization shows ORF9b homodimer has ~22 kDa and random coil conformation, while the ORF9b-TOM70 complex is folded and more thermally stable than free TOM70. |
SEC-MALS, circular dichroism, differential scanning calorimetry, protein-protein interaction assay (co-expression and co-purification), pull-down |
Biochimie |
Medium |
35643212
|
| 2025 |
Using cryo-EM, 19F NMR, and ITC, Orf9b inhibits Hsp90 binding to Tom70 through a bipartite steric-blocking mechanism: the helix and intrinsically disordered tail of Orf9b sterically block two distinct structural units of Hsp90 from accessing Tom70. Orf9b primarily slows the association kinetics between Hsp90 and Tom70, rather than acting through allosteric conformational changes in Tom70. |
Cryo-electron microscopy, 19F NMR spectroscopy, isothermal titration calorimetry, kinetic binding analysis |
bioRxivpreprint |
High |
41332678
|
| 2025 |
In yeast meiosis, Tom70 concentrates around the Gametogenesis-Uninherited Nuclear Compartment (GUNC) and tethers mitochondria to the nuclear envelope by recruiting the tethering protein Cnm1, independently of its canonical mitochondrial import function. Loss of Tom70 disrupts sequestration of nuclear pore complexes into the GUNC, and loss of Cnm1 partially phenocopies tom70Δ. |
Fluorescence live-cell imaging, gene deletion (tom70Δ, cnm1Δ), genetic epistasis, subcellular fractionation |
bioRxivpreprint |
Medium |
41332789
|
| 2023 |
ASFV protein p17 promotes mitophagy by facilitating the interaction of autophagy receptor SQSTM1 with TOMM70. Co-immunoprecipitation/mass spectrometry identified TOMM70 as a p17-interacting protein. The p17-TOMM70 interaction enhances SQSTM1 binding to TOMM70, leading to mitochondrial engulfment by autophagosomes and degradation of mitochondrial antiviral signaling proteins. |
Co-immunoprecipitation/mass spectrometry, co-immunoprecipitation, mitophagy assay (autophagosome engulfment, mitochondrial counts), siRNA knockdown |
Virulence |
Medium |
37442088
|
| 2014 |
Tom70 downregulation in pathological hypertrophic hearts causes defective mitochondrial import of OPA1, triggering intracellular oxidative stress and pathological cardiac hypertrophy. Overexpression of Tom70 confers resistance to pro-hypertrophic insults. Tom70 thus acts as a molecular switch orchestrating hypertrophic stress and mitochondrial responses. |
siRNA knockdown and lentiviral overexpression in vivo/in vitro, mitochondrial import assay for OPA1, ROS measurement, echocardiography |
Cell research |
Medium |
25022898
|
| 2020 |
De novo loss-of-function variants in TOMM70 (p.Thr607Ile, p.Ile554Phe) cause neurological impairment. In a Drosophila model replacing Tom70 with human TOMM70, both variants provided significantly less rescue of lethality than reference TOMM70. RNAi knockdown of Tom70 in the developing eye caused roughening and synaptic transmission defects rescued by reference but not variant TOMM70. |
CRISPR-Cas9 humanized Drosophila model, UAS-GAL4 rescue assay, RNAi knockdown, synaptic transmission electrophysiology |
Human molecular genetics |
Medium |
32356556
|
| 2017 |
Tom70 governs the mitochondrial localization of MICU1 (mitochondrial Ca2+ uptake regulator). Tom70 knockdown reduces mitochondrial MICU1 content, worsens MI/R-induced mitochondrial Ca2+ overload, and exacerbates myocardial injury. Tom70 overexpression preserves mitochondrial MICU1, which is required for Tom70's cardioprotective effects. |
siRNA knockdown, lentiviral overexpression, mitochondrial fractionation, Ca2+ measurement, in vivo MI/R mouse model |
Cell death & disease |
Medium |
28703803
|
| 2024 |
Proximity labeling (APEX2) shows that human TOMM70 and TOMM20 have differential association profiles with RNA-binding proteins (RBPs) and translation factors, with several RBPs (including SYNJ2BP) preferentially associating with TOMM20 over TOMM70. During translation stress (puromycin), RBP association increases specifically with TOMM20, suggesting TOMM70 does not share this role in preserving hemostasis during translation stress. |
APEX2-based proximity labeling, quantitative mass spectrometry, puromycin translation inhibition |
bioRxivpreprint |
Medium |
bio_10.1101_2024.10.25.620316
|